73-87 Rear Disc Brake Conversion Problem

[SmokinB]

might not be the right volumes being used
Maybe a brake line diameter or bad piston seal(s) situation
The front calipers are still the original non-low drag brakes right? Hows your pushrod lengths

I assume you have rubber whips from the steel lines to the calipers. These can cause sponginess. If your not using a very stiff steel braided whips you may want to switch them.

I've had this same problem and this was my fix.

I've never paid attention to brake line size but intuition tells me that if they are not the same size the larger lines should feed the more important front brakes.

 

[Blazerbiker]

I'd second the 1 1/8" master. 1" will give you a pretty long pedal stroke.

 

[AuroraGirl]

Might be a dumb question, but do these rear calipers use pads like the fronts? So there is a clinching procedure for the outboard pad but not the inboard pad?

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[Ricko1966]

Hi All,
I have a '78 Stepside and i bought a Cadillac Eldorado rear brake conversion kit to upgrade my truck. Unfortunately, I cannot get the brakes to firm up after bleeding. I understand they are notoriously hard to bleed and I either still have air in them or i've got a missmatch of hardware.
This is the hardware I am running:
*JEGS Rear Disk Brake Conversion 965-TRD4745
*JEGS Disc/Disc Proportioning Valve 555-631292
*The Right Stuff DBMC05 Disc/Disc Master Cylinder (1" bore)
*Brake lines are factory. 1/8" front, 1/4" rear
*Front brakes are stock calipers
*All new soft brake lines

I changed out the out the original Disc/Drum master cylider and proportioning valve but I cant get the brake pedal to firm up after many, many attempts to get them bled.

When it comes to bleeding I've tried gravity, brake pedal pumping, and a vacuum bleed system that I purchased. I've always positioned the bleed valve at the highest spot and even gone so far as to tap the rears with a hammer to knock loose any air if it was trapped in the rears. I've even taken the rears loose while vacuum bleeding, tapping them with a hammer and roating them to try and remove any trapped air. Finally, I have an ASE Certified Mechanic best buddy come over and we rebled the entire system starting at the master cylinder we bled each component only to continue to have a soft pedal.

If I pinch off the rear center bake line so only the front brakes are involved, the pedal is firm. This confirms the problem is in the rear.

I could really use some help. Do I have the right Master Cylider and Proportioning Valve? I find it hard to believe I still have air in the system. I've bled them no less than 20 times and i've been bleeding brakes for 20 years. Thanks for your feedback!

Does the truck have power brakes or manual brakes. Did it always have that type?

 

[AuroraGirl]

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